"The lawyers had to go back and forth with U.S. Immigration for several months to get everything in place, especially understanding that this is a sport," Michael O'Dell, Dignitas' manager, told the BBC.

To qualify for a P-1 visa, one has to demonstrate "a high level of achievement in a field evidenced by a degree of skill and recognition substantially above that ordinarily encountered, to the extent that such achievement is renowned, leading, or well-known in more than one country," according to the United States Citizenship and Immigration Services.